The present invention relates to a moving catalyst bed reactor for the catalytic treatment of hydrocarbons, particularly the catalytic desulphurization and de-metallization of petroleum residues.
Moving catalyst bed reactors are known, e.g., as described in U.S. Pat. No. 3,883,312, issued May 13, 1975, by Youngman, which disclosure is incorporated herein by reference. According to the patent, both the used solid catalyst and the reactor effluent are removed from a moving catalyst bed reactor through the same withdrawal conduit. The reactor effluent leaves the conduit through the openings of a circumferential screen section in its wall. The catalyst descends past the openings and is washed by an upward moving oil which leaves the conduit through the same openings.
In recent years there is a tendency to carry out processes of the kind mentioned on an ever increasing scale. However, this scale-up to large capacities creates problems in the construction and design of the reactors. One such problem is that the diameter of the vertical outlet channel must be increased to allow the larger mass of catalyst to pass the channel. As a consequence, the diameter of the circumferential screen section must be increased, thereby complicating the manufacture and installation of the screen section. Furthermore, enlargment of the diameter of the cylindrical screen section will soon lead to the problem that the screen section as a whole can no longer be removed from the interior of the vessel through the normally available manholes in the reactor wall. This means, that, for repair or replacement of the screen section, it is necessary to split the screen section into a number of parts, or to dismantle the reactor, both of which are time-consuming operations.
A further consequence of the growing tendency to carry out catalytic treating processes on an increased scale is the fact that the screen sections in the outlet channels of the reactors must withstand ever increasing loads both in horizontal and vertical directions. In at least some prior art moving catalyst bed reactors, the screen sections in the vertical channels form an integral part of the vertical channels, and must therefore withstand the load of the catalyst. This means that in these moving catalyst bed reactors the size and number of the openings in the screen sections are to be reduced or extra reinforcing means are to be applied to obtain the required resistance of the screen sections against increasing loads. Reducing the size and/or number of openings has an adverse influence on the separating efficiency of the vertical outlet channels. Accordingly, it is an object of the invention to overcome these difficulties.